I can't vouch for the LRP28 S3 yet. I only have about two gallons through it in my aftershock. I have significantly more power on tap than my buddy who has an LST2 with the stock engine and aftermarket pipe.
The reason I can't vouch for it is because I wouldn't feel right saying it's a really great engine until I know how long it lasts. It runs great, has a ton of power, but if it craps out at 4 gallons, I wouldn't buy another and I wouldn't recommend it to anyone.
The first 1/2 gallon was kind of rough going. It likes 25% nitro better than 20% I started break-in with. After about 3/4 gallon, I started leaning it for better performance. After a gallon I've just tweaked it a little here and there depending on the weather.
It runs like a top now. Starts right up, runs around 210F-240F with gobs of power. I did the trans gear swap mod because I'm running t-maxx sized tires, so I lost a bit of top speed. With the LRP and gear swap, I can chase down my friend with his LST2 with relative ease. The hardest part for me is off the line. I have to feather the throttle a ridiculous amount to keep it from going on it's roof.
Here's a vid of mine rolling around showing how easy wheelies are:
[ame="http://www.youtube.com/watch?v=ex7OCovM5iI"]YouTube - Lrp 28 Spec3 in an Losi Aftershock[/ame]